Introduction
The Aegilops genus contains species closely related to wheat. Electrophoretic analyses of seed storage proteins – glutenins and gliadins – have proven very useful in evaluating and characterizing of jointed goatgrass (Aegilops cylindrica Host.) accessions. Jointed goatgrass has C and D genomes. High molecular weight-glutenin subunits (HMW-GS) are controlled by genes at two complex loci – Glu-1C and Glu-1D – located on the long arm of the group 1 chromosome. Different allelic subunits at each Glu-1 locus have been identified by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Each Glu-1 complex locus consists of two tightly linked but not always expressed genes (Payne et al., Reference Payne, Holt and Law1981). Within the loci, recombination is rare. In diploid species, both subunits are expressed, whereas in polyploid species such as wheat and jointed goatgrass, there is silencing of one or more subunits (Payne et al., Reference Payne, Holt and Law1981; Galili and Feldman, Reference Galili and Feldman1983). Jointed goatgrass has a three-band pattern due to non-expression of the Glu-1Dx subunit (Johnson, Reference Johnson1967).
Materials and methods
We analysed six accessions of A. cylindrica populations collected from the Slovak Republic. HMW-GS were extracted from randomly selected single seeds, and protein was extracted from the non-embryo half of the seed. Extractions, electrophoretic separation of glutenin and detection procedures used were in accordance to International Seed Testing Association (ISTA) standard procedure for SDS-PAGE, and glutenin subunits were identified following the catalogue of HMW-GS alleles (Payne and Lawrence, Reference Payne and Lawrence1983). Gliadin in the genotypes was examined using acid PAGE according to the standard ISTA reference method (Bushuk and Zillman, Reference Bushuk and Zillman1978).
Results and discussion
The x- and y-type subunits of the respective C and D genome band contributions to the HMW glutenin pattern for jointed goatgrass were identified by comparison with the band pattern of Triticum aestivum cv. Chinese Spring. The Glu-1 subunit assignment system developed by Payne and Lawrence (Reference Payne and Lawrence1983) was used to identify the relative band positions for the Glu-1A, Glu-1B and Glu-1D subunits. Glu-1C alleles are not encompassed in this assignment system. Jointed goatgrass has a three-band HMW glutenin pattern with a CxCyDy subunit composition and is in agreement with the assignments determined by Wan et al. (Reference Wan, Liu, Wang and Shewry2000). Glu-1Dx subunit was not expressed in all tested material. This low variation for the Glu-1 genetic marker was consistent with other findings of low genetic diversity in jointed goatgrass (Okuno et al., Reference Okuno, Ebana, Noov and Yoshida1998). Gliadin electrophoresis (Fig. 1) showed a higher level of polymorphism than glutenin and therefore should be better for use in population identification. Gliadins are a highly polymorphic and biochemically unusual class of proteins characterized by very complex electrophoretograms when separated under acid conditions. Traditionally, the electrophoretograms of gliadins are divided into α, β, γ and ω zones, with proteins found in each zone being grouped into separate subclasses. The ω gliadins have a low cysteine content, differing from the other groups of gliadins, which are cysteine-rich (Shewry and Tatham, Reference Shewry and Tatham1990). We identified γ, δ and ω zones of gliadins in the jointed goatgrass populations, but not α. The highest variation in gliadin bands among the populations was from Cierna nad Tisou, with five different compositions. There were small differences among the populations from Chlaba and Dobra, with three different gliadin compositions. The lowest variations were from Sered and Dunajska Streda populations, with only two different compositions. The present investigation showed that the jointed goatgrass populations collected from Slovakia were valuable genetic resources for wheat crop improvement programmes.
Fig. 1 Gliadin pattern of Slovak accessions in jointed goatgrass (A. cylindrica Host.): lanes 1–3, populations from Chlaba; lanes 4, 5, populations from Sered; lanes 6, 7, populations from Dunajska Streda; lines 8–10, populations from Kamenica nad Hronom; lanes 11–17, populations from Cierna nad Tisou; lanes 19–20, populations from Dobra.
Acknowledgements
This work was supported by the Slovak Research and Development Agency under the contract no. APVV-0770-07.
